The invention relates to a method and apparatus for machining by electrical discharges an electrode workpiece by means of an electrode tool, wherein a liquid fluid, having electrically conductive particles which are suspended in the liquid, is introduced in the machining zone between the electrodes, and consecutive voltage pulses are applied between the electrodes for triggering the electrical discharges. The process and apparatus of the invention permit high precision control of the width of the electrical discharge gap between the electrode workpiece and the electrode tool in an EDM apparatus.
The accuracy of machining by EDM a cavity in a workpiece by means of an electrode tool is essentially dependent upon the accuracy of the limit of feed of the electrode tool and the width of the gap at the moment at which machining is stopped. Diverse solutions have been proposed in the past for solving the problem presented by electronically controlling, with high precision, the relative position of the electrodes and for decreasing the rate of wear of the electrode tool in the course of a finishing pass. However, the gap may vary very widely according to the voltaic couple presented by the material compositions of the workpiece and of the electrode tool, the machining rate and the rate of contamination of the machining fluid. Those variable factors have all a direct influence upon the precision and accuracy of machining.